Simplify USB‑PD 1‑4S Charging with ROHM BD99954 Buck/Boost IC

The BD99954 is a versatile buck/boost battery manager from ROHM that charges a battery using standard USB‑PD voltages and can reverse‑provide power to external loads.

The BD99954 is available in a 40‑pin QFN (0.4 mm pitch, 5 mm × 5 mm, BD99954MWV) and a wafer‑level CSP (41‑ball, 0.4 mm pitch, 2.6 mm × 3 mm, BD99954GW). These packages are designed for space‑constrained mobile devices. In this tutorial we demonstrate two real‑world use cases: charging a simulated battery from a USB‑PD supply and powering a load from the same IC.

We use the BD99954 eval kit, which employs the QFN package and includes the following key specifications from the datasheet:

For better reference, view the eval kit image below:

Demo #1 – Battery Charging

In this demo, the BD99954 charges a simulated battery. A 15 V power supply is connected to the B‑bus, an SMU is set to 5.5 V sync to emulate a depleted two‑cell battery, and a DMM monitors VSys to verify a constant system output. The 15 V supply demonstrates that the IC can handle any USB‑PD standard voltage.

Demo #2 – Load Powering from Battery

Software controls the BD99954’s parameters. The bus current limit is set to 1.5 A and the charging profile is JEITA‑compliant. VSYSREG is pre‑charged to ~7 V, the threshold to 6 V, and the fast‑charge regulator to 8.4 V. As the simulated battery voltage rises, the IC steps through each charging stage, delivering the appropriate current.

Conclusion

The BD99954 provides a single power path that both charges and powers devices at standard USB‑PD voltages. It supports USB Type‑C, 1‑4 cell batteries, and integrates seamlessly with ROHM’s USB‑PD and wireless charging solutions. For datasheets and further details, visit ROHM.com.

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